Field
This disclosure relates to an image display method, an image display apparatus, and a storage medium.
Description of the Related Art
As a method of acquiring a tomographic image of an object to be measured, e.g., a living body, in a non-destructive and non-invasive manner, optical coherence tomography (hereinafter referred to as “OCT”) has been put into practical use. OCT is widely used particularly in the field of ophthalmology in order to acquire a tomographic image of a retina in a fundus of an eye to be inspected for ophthalmologic diagnosis of the retina, or the like.
In OCT, light reflected from the object to be measured and light reflected from a reference mirror are caused to interfere with each other, and time dependence or wavenumber dependence of an intensity of the interference light is analyzed, to thereby acquire a tomographic image. As apparatus for acquiring such an optical coherence tomographic image, there are known a time domain OCT apparatus, a spectral domain OCT apparatus, and a swept source OCT apparatus. The time domain OCT apparatus is configured to acquire depth information on the object to be measured by changing a position of the reference mirror. The spectral domain optical coherence tomography (SD-OCT) apparatus using a broadband light source is configured to split interference light into light beams having different wavelengths with a spectroscope to acquire depth information on the object to be measured. The swept source optical coherence tomography (SS-OCT) apparatus is configured to use a wavelength-tunable light source apparatus capable of changing an oscillation wavelength. The SD-OCT and the SS-OCT are collectively referred to as “Fourier domain optical coherence tomography (FD-OCT)”.
In recent years, there has been proposed simulated angiography using FD-OCT, which is referred to as “OCT angiography (OCTA)” (Makita et al., “Optical Coherence Angiography,” Optics Express, 14(17), 7821-7840 (2006)). In fluorescence angiography, which is general angiography in contemporary clinical medicine, injection of a fluorescent dye (e.g., fluorescein or indocyanine green) into a body is required, and a vessel through which the fluorescent dye passes is displayed two-dimensionally. Meanwhile, OCTA enables non-invasive and simulated imaging of vessels, and enables three-dimensional display of a network of a blood flow region. Further, OCTA is attracting attention because OCTA provides a higher resolution as compared with fluorescence angiography, which enables a minute vessel or blood flow of the fundus to be drawn.
There have been proposed a plurality of methods for OCTA, which differ in blood flow detection method. For example, in “An et al. ‘Optical microangiography provides correlation between microstructure and microvasculature of optic nerve head in human subjects,’ J. Biomed. Opt. 17, 116018 (2012)”, there is proposed a method involving extracting only a signal that is changing in time from OCT signals, to thereby obtain an OCT signal due to a blood flow. In “Fingler et al. ‘Mobility and transverse flow visualization using phase variance contrast with spectral domain optical coherence tomography’ Optics Express. Vol. 15, No. 20. pp. 12636-12653 (2007)”, there is proposed a method using a phase variance due to a blood flow. In each of “Mariampillai et al., ‘Optimized speckle variance OCT imaging of microvasculature,’ Optics Letters 35, 1257-1259 (2010)” and U.S. Patent Application Publication No. 2014/221827, there is proposed a method using an intensity variance due to a blood flow.
However, in the above-mentioned OCTA, a blood flow region can be acquired in detail, and hence, an inspector may have difficulty in identifying a connection of a specific vessel of interest and how the specific vessel extends. Further, an image relating to the blood flow region acquired through the above-mentioned OCTA and an image relating to the structure information acquired through OCT are acquired as independent and separate images. Thus, in actual diagnosis, the inspector needs to compare those images with each other alternately. However, because the detailed blood flow region acquired through OCTA is displayed in detail, its correspondence to structure information on the eye to be inspected that is acquired from an OCT intensity image, a fundus photograph, or the like, is difficult to understand.
This disclosure has been made in view of the above-mentioned circumstances, and it is an object of this disclosure to facilitate understanding of correspondence between an image relating to a blood flow region acquired through OCTA and structure information acquired through OCT, or the like.
In order to solve the above-mentioned problem, one aspect of the present invention is an image display method comprising the steps of acquiring a first image within a first area of an object to be inspected, acquiring interference signal sets corresponding to a plurality of frames, which are acquired with an intention to acquire the same cross section, for a plurality of different cross sections, generating, based on the interference signal sets corresponding to the plurality of frames, a motion contrast image within a second area included in the first area, and superimposing, for display, information acquired from a part of the motion contrast image onto a corresponding position of the first image.
According to this disclosure, understanding of the correspondence between the image relating to the blood flow region acquired through OCTA and the structure information acquired through OCT, or the like, can be facilitated.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.